package scheduler

import (
	"context"
	"sort"
	"time"
)

// MigrationType represents different types of migrations
type MigrationType int

const (
	MigrationNormal MigrationType = iota
	MigrationBatch
	MigrationPredictive
	MigrationEmergency
)

// MigrationPlan represents a planned set of migrations
type MigrationPlan struct {
	ID         string
	Type       MigrationType
	Migrations []*TaskMigration
	TotalCost  float64
	StartTime  time.Time
	EndTime    time.Time
	Status     string
	Priority   int
	Metadata   map[string]interface{}
}

// MigrationPredictor predicts future system state
type MigrationPredictor struct {
	scheduler  *Scheduler
	history    []*MigrationHistory
	confidence float64
}

// SystemState represents system state at a point in time
type SystemState struct {
	Timestamp     time.Time
	AgentLoads    map[string]float64
	TaskCount     int
	ResourceUsage map[string]float64
}

// BatchMigrationStrategy handles batch migrations
type BatchMigrationStrategy struct {
	maxBatchSize      int
	cooldownPeriod    time.Duration
	lastMigrationTime time.Time
	scheduler         *Scheduler
}

// NewBatchMigrationStrategy creates a new batch migration strategy
func NewBatchMigrationStrategy(scheduler *Scheduler, maxBatchSize int, cooldown time.Duration) *BatchMigrationStrategy {
	return &BatchMigrationStrategy{
		maxBatchSize:   maxBatchSize,
		cooldownPeriod: cooldown,
		scheduler:      scheduler,
	}
}

// PlanBatchMigration plans a batch migration
func (b *BatchMigrationStrategy) PlanBatchMigration(ctx context.Context) (*MigrationPlan, error) {
	// Check cooldown period
	if time.Since(b.lastMigrationTime) < b.cooldownPeriod {
		return nil, ErrCooldownPeriod
	}

	// Get migration candidates
	candidates := b.scheduler.GetMigrationCandidates()
	if len(candidates) == 0 {
		return nil, ErrNoMigrationNeeded
	}

	// Sort candidates by priority and cost
	sort.Slice(candidates, func(i, j int) bool {
		if candidates[i].Priority != candidates[j].Priority {
			return candidates[i].Priority > candidates[j].Priority
		}
		return candidates[i].Cost < candidates[j].Cost
	})

	// Create batch plan
	plan := &MigrationPlan{
		ID:        generateID(),
		Type:      MigrationBatch,
		StartTime: time.Now(),
		Status:    "planned",
		Metadata:  make(map[string]interface{}),
	}

	// Add migrations to plan up to batch size
	totalCost := 0.0
	for i, candidate := range candidates {
		if i >= b.maxBatchSize {
			break
		}
		plan.Migrations = append(plan.Migrations, candidate)
		totalCost += candidate.Cost
	}

	plan.TotalCost = totalCost
	return plan, nil
}

// ExecuteBatchMigration executes a batch migration plan
func (b *BatchMigrationStrategy) ExecuteBatchMigration(ctx context.Context, plan *MigrationPlan) error {
	// Validate plan
	if plan.Type != MigrationBatch {
		return ErrInvalidPlanType
	}

	// Execute migrations in parallel with error handling
	errChan := make(chan error, len(plan.Migrations))
	for _, migration := range plan.Migrations {
		go func(m *TaskMigration) {
			err := b.scheduler.MigrateTask(m.TaskID, m.FromAgent, m.ToAgent)
			errChan <- err
		}(migration)
	}

	// Collect errors
	var errors []error
	for i := 0; i < len(plan.Migrations); i++ {
		if err := <-errChan; err != nil {
			errors = append(errors, err)
		}
	}

	// Update plan status
	plan.EndTime = time.Now()
	if len(errors) > 0 {
		plan.Status = "failed"
		plan.Metadata["errors"] = errors
		return ErrBatchMigrationFailed
	}

	plan.Status = "completed"
	b.lastMigrationTime = time.Now()
	return nil
}

// PredictiveMigrationStrategy handles predictive migrations
type PredictiveMigrationStrategy struct {
	scheduler *Scheduler
	predictor *MigrationPredictor
	threshold float64
	lookAhead time.Duration
}

// NewPredictiveMigrationStrategy creates a new predictive migration strategy
func NewPredictiveMigrationStrategy(scheduler *Scheduler, threshold float64, lookAhead time.Duration) *PredictiveMigrationStrategy {
	return &PredictiveMigrationStrategy{
		predictor: &MigrationPredictor{},
		scheduler: scheduler,
		threshold: threshold,
		lookAhead: lookAhead,
	}
}

// PredictLoadChanges predicts future system load
func (p *PredictiveMigrationStrategy) PredictLoadChanges(ctx context.Context) map[string]float64 {
	predictions := make(map[string]float64)
	systemLoad := p.scheduler.GetSystemLoad()

	// Analyze historical data
	for agentID := range systemLoad["agent_loads"].(map[string]int) {
		predictedLoad := p.predictor.predictAgentLoad(agentID)
		predictions[agentID] = predictedLoad
	}

	return predictions
}

// PlanPredictiveMigration plans migrations based on predictions
func (p *PredictiveMigrationStrategy) PlanPredictiveMigration(ctx context.Context) (*MigrationPlan, error) {
	predictions := p.PredictLoadChanges(ctx)

	// Find agents predicted to be overloaded
	var overloadedAgents []string
	for agentID, predictedLoad := range predictions {
		if predictedLoad > p.threshold {
			overloadedAgents = append(overloadedAgents, agentID)
		}
	}

	if len(overloadedAgents) == 0 {
		return nil, ErrNoMigrationNeeded
	}

	// Create migration plan
	plan := &MigrationPlan{
		ID:        generateID(),
		Type:      MigrationPredictive,
		StartTime: time.Now().Add(p.lookAhead),
		Status:    "planned",
		Metadata: map[string]interface{}{
			"predictions":       predictions,
			"confidence":        p.predictor.confidence,
			"prediction_window": p.lookAhead,
		},
	}

	// Plan migrations for predicted overloads
	for _, agentID := range overloadedAgents {
		tasks := p.scheduler.getAgentTasks(agentID)
		for _, task := range tasks {
			if targetAgent := p.findBestTargetAgent(task, predictions); targetAgent != "" {
				migration := &TaskMigration{
					TaskID:    task.ID,
					FromAgent: agentID,
					ToAgent:   targetAgent,
					Priority:  TaskPriority(task.Priority),
					Timestamp: plan.StartTime,
				}
				plan.Migrations = append(plan.Migrations, migration)
			}
		}
	}

	return plan, nil
}

// EmergencyMigrationStrategy handles emergency migrations
type EmergencyMigrationStrategy struct {
	scheduler         *Scheduler
	criticalThreshold float64
	maxRetries        int
}

// NewEmergencyMigrationStrategy creates a new emergency migration strategy
func NewEmergencyMigrationStrategy(scheduler *Scheduler, threshold float64) *EmergencyMigrationStrategy {
	return &EmergencyMigrationStrategy{
		scheduler:         scheduler,
		criticalThreshold: threshold,
		maxRetries:        3,
	}
}

// HandleEmergency handles emergency situations
func (e *EmergencyMigrationStrategy) HandleEmergency(ctx context.Context, agentID string) error {
	// Get agent's tasks
	tasks := e.scheduler.getAgentTasks(agentID)
	if len(tasks) == 0 {
		return nil
	}

	// Create emergency plan
	plan := &MigrationPlan{
		ID:        generateID(),
		Type:      MigrationEmergency,
		StartTime: time.Now(),
		Status:    "emergency",
		Priority:  10, // Highest priority
	}

	// Sort tasks by priority
	sort.Slice(tasks, func(i, j int) bool {
		return tasks[i].Priority > tasks[j].Priority
	})

	// Try to migrate each task
	for _, task := range tasks {
		// Find any available agent
		for targetID := range e.scheduler.agents {
			if targetID != agentID && e.scheduler.checkAgentCapacity(targetID, task) {
				migration := &TaskMigration{
					TaskID:    task.ID,
					FromAgent: agentID,
					ToAgent:   targetID,
					Priority:  TaskPriority(task.Priority),
					Timestamp: time.Now(),
				}
				plan.Migrations = append(plan.Migrations, migration)
				break
			}
		}
	}

	// Execute emergency migrations immediately
	return e.executeEmergencyPlan(ctx, plan)
}

// executeEmergencyPlan executes an emergency migration plan
func (e *EmergencyMigrationStrategy) executeEmergencyPlan(ctx context.Context, plan *MigrationPlan) error {
	var lastError error
	for _, migration := range plan.Migrations {
		// Try multiple times for each migration
		for retry := 0; retry < e.maxRetries; retry++ {
			err := e.scheduler.MigrateTask(migration.TaskID, migration.FromAgent, migration.ToAgent)
			if err == nil {
				break
			}
			lastError = err
			time.Sleep(time.Millisecond * 100 * time.Duration(retry+1))
		}
	}
	return lastError
}

func (p *MigrationPredictor) predictAgentLoad(agentID string) float64 {
	// Implementation
	return 0.0
}

func (p *PredictiveMigrationStrategy) calculatePredictionConfidence() float64 {
	// Implementation
	return 0.0
}

func (p *PredictiveMigrationStrategy) findBestTargetAgent(task *Task, predictions map[string]float64) string {
	// Implementation
	return ""
}

// MigrationHistory represents the history of a migration
type MigrationHistory struct {
	// ... 必要的字段
}

// 使用 types.go 中定义的 TaskPriority
const (
	LowPriority    = PriorityLow
	MediumPriority = PriorityMedium
	HighPriority   = PriorityHigh
)
